A so-called structured packaging film is used typically to make a bag, for instance a bag holding a specific product.
Such bags as well as for example tray packaging having a cover film, are generally provided, at least on visible surfaces with indicia for furnishing information to a user and for creating a high-quality appearance with printing. The indicia may indicate what is held in the bag, or merely identify a merchant or even an advertiser In addition, for further improving the appearance it is also known to provide the packaging film, which in itself is planar and flat, with structuring, that is with indicia that are raised above the generally flat surface of the bag. In particular, individual areas may be emphasized via appropriately adapted structuring that does not recur over the entire surface area. For example, individual text fields, images, logos, as well as finer structures such as outlines and letters may be emphasized.
To achieve a high-quality 3D effect in a packaging film, according to EP 2 347 967 it is known to emboss the packaging film, it then being possible to also align the embossed pattern or indicia with a print pattern. For example, raised areas are engaged with an ink roller so that only these areas are inked.
For embossed packaging films, however, there is the disadvantage that the embossing effect becomes reduced over time due to the elastic recovery behavior of the polymer chains. This reduction is accelerated in particular when pressure is exerted on the packaging film, and/or the packaging film is stored at an elevated temperature.
Furthermore, there is also the risk that embossed areas may be easily pressed flat if enough force is applied. It must also be taken into account that embossing, in particular when it is adapted to a specific design or printed image of the bag, is done directly during manufacture of the film, the packaging film then being rolled up for transport and storage. Merely the bearing pressure on a roller may result in a reduction of the embossment.
These disadvantages may be avoided when, according to EP 2 272 647, a packaging film is formed that is still embossable in areas after the extrusion process. However, the subsequent activation of such a packaging film is relatively complicated, and in addition high manufacturing costs result due to the incorporation of foamable particles. It is also disadvantageous that in principle the entire surface area of the packaging film is available for embossing, but ultimately only small areas are actually embossed.